RFID systems are well known in the art. Such systems include relatively large packages containing battery powered transmission/receiving circuitry, such as the identification system disclosed in U.S. Pat. No. 4,274,083, to passive systems in which the transceiver receives its power from the base station or interrogator, such as the identification system disclosed in U.S. Pat. No. 4,654,658.
A typical RFID system is made up of reusable tags fixed to or embedded in product carriers, RFID read or RFID read/write antenna units that communicate with the tags via a RF link and a controller. The host (or computer) system interfaces with the controller and directs the interrogation of the tags.
The RFID system thus provides effective means of identifying, monitoring and controlling materials in a closed loop process. In a factory environment, the tags are employed as the transport mechanism between "islands of automation," providing a record of each process which can be acted upon immediately or downloaded later for analysis.
In operation, as a tag passes near a RFID antenna unit, an antenna emits RF signals towards the tag. The emitted RF signals induce a current in the tag. The current powers-up the tag, thereby enabling the tag to transmit response signals from the tag to the antenna unit.
The tags can also be powered by an internal battery (i.e., an "active" tag). The life span of an active tag is, however, generally limited by the lifetime of the battery.
Commonly, RFID antenna units are placed on standard mountings built into the manufacturing facility. These standard mountings are located throughout the manufacturing facility wherever monitoring devices may be needed.
Often, the mountings require that the RFID antenna unit(s) be placed into cramped locations. Thus, conventional RFID antenna units are typically separated into two distinct portions, a unidirectional antenna portion and the read/write electronics portion. The two distinct portions of the unit are connected to each other by, for example, a cable or other extended electrical connector. Such cable or other extended electrical connectors crowd the manufacturing environment, serve as a source of power loss, and are a source of electrical noise. In addition to the noise generated by the cable or other extended electrical connectors, noise is also generated by the reader power supply. The generated noise can make it difficult to receive clear response signals transmitted by the tagged item.
In addition to the problems associated with cables or other extended electrical connectors, in many instances, due to the placement of the standard mountings, numerous uni-directional antenna units must be located in close proximity to the path of the item to be monitored. That is, because the antenna portion is attached to standard mountings, the uni-directional antenna unit may not always be focused directly towards the path of the tagged item. Thus, in order to insure that the tag disposed on an item is incident with the RF signals emitted from the unidirectional antenna, several antenna units are required.
Several approaches have been employed to address the aforementioned problems associated with conventional RFID systems, employing a unidirectional antenna. Illustrative is the RFID reader unit disclosed in U.S. Pat. No. 5,621,199, assigned to Escort Memory Systems, Scotts Valley, Calif.
In U.S. Pat. No. 5,621,199, a RFID reader unit is disclosed having an antenna containing head portion and read/write electronics-containing body portion integrated into a single, compact structure. The antenna-containing head portion is also rotatably adjustable to enhance the unidirectional antenna coverage. The noted head and, hence, antenna adjustment is however achieved manually.
It is therefore an object of the present invention to provide a multi-directional antenna which can be readily employed in a RFID unit to enhance RF transmission coverage.
It is a further object of the present invention to provide a multi-directional antenna which can be employed in a RFID unit and readily focused in a multitude of directions.
It is yet another object of the present invention to provide a multi-directional antenna which can be employed in a RFID unit to eliminate the need for numerous additional RFID antenna units.